Wobble information detection method and wobble information detection apparatus for optical recording medium

ABSTRACT

A method and apparatus for detecting information recorded as a phase-modulated wobble along a track of an optical disk, whereby a reference phase section is recorded with wobble having a predetermined reference phase and whereby respective polarities of phase integration values obtained by synchronous detection of phase-modulated unit sections following the reference phase section, in a playback wobble signal, are compared with the polarity of a reference phase integration value obtained for the reference phase section, to thereby detect respective bit states expressed by the phase-modulated unit sections.

BACKGROUND OF THE INVENTION

[0001] 1. Field of Application

[0002] The operation relates to a wobble information detection methodand apparatus for operating on a wobble signal that is read from anoptical recording medium, which in general is an optical recording disk.

[0003] In particular, the apparatus relates to a wobble informationdetection method and apparatus whereby reliable detection can beachieved for information that has been recorded by phase modulation of awobble that is formed along a track of the optical recording medium.

[0004] 2. Background of the Invention

[0005] There are various standards and recording formats for playbacktypes of optical recording medium such as a CD (compact disk), DVD(digital versatile disk), etc., and for write-once types of opticalrecording medium such as a CD-R (rewritable CD), DVD-R, etc., and forrewritable types of optical recording medium such as a DVD-RAM(random-access memory DVD), DVD-RW (rewritable DVD), etc.

[0006] In the case of a write-once type of optical recording disk suchas a CD-R for example, as seen in the partial view of the lower side ofsuch an optical recording disk 50 shown in FIG. 7, a track is formedalong a groove 51 which wobbles laterally with a fixed periodic ofvariation, with that wobble-shaped groove being referred to in thefollowing simply as the “wobble”. A playback signal from an opticalpick-up (not shown in the drawing) which reads data from the track alsoderives a signal (referred to in the following as the wobble signal)from the wobble, with that wobble signal having a specific frequency(standardized as 22.05 kHz). In the following, only playback of thewobble signal will be considered.

[0007] The wobble is recorded by being phase modulated with informationsuch as track address information (ATIP), indicating the absolutepositions of tracks. In an optical disk recording/playback apparatus(referred to in the following simply as an optical disk apparatus), anoptical pick-up forms a focused light spot (indicated by numeral 52 inFIG. 7) onto a track and derives a wobble signal from the resultantreflected light. The wobble signal is then demodulated, and theaforementioned recorded information from the demodulated wobble signalis used by the optical disk apparatus in generating a disk rotationcontrol signal during a recording or playback operation, and to generatea reference clock signal.

[0008] In the case of a DVD-R or DVD-RAM, on the other hand, the wobbledoes not consist of an actual shape variation of the tracks, with thewobble information instead being recorded as pits on the land side of atrack. With such a method, no modulation is applied to the wobble, andthe wobble signal is used to set a clock frequency (140 kHz) for diskrotation control.

[0009] Considering the wobble that is recorded by the phase modulationmethod, the phase is inverted to indicate respective bit states (e.g.,with the 0° phase indicating the “1” bit state, and the 180° phaseindicating the “0” bit state). The optical disk apparatus applies phasediscrimination to the wobble signal to thereby demodulate theaforementioned recorded information.

[0010] One method of demodulation of the wobble signal is described forexample in Japanese patent Laid-open No. 2002-208231 (page 2, FIG. 7).With that method, a threshold value is established with respect to thewobble signal, for use in detecting the phase inversions. By judging thenumber of times that the wobble signal is inverted within a fixed unitinterval, the “0” and “1” bit states can be discriminated, asillustrated in the example of FIGS. 8A, 8B in which phase modulation ofa wobble signal expresses a “0” and a “1” bit, respectively, with themodulation performed in units of 8 periods of the wobble signal. Byusing two threshold values designated as Vt1, Vt2 respectively forthreshold level comparison, the number of phase inversions which occurwithin a unit interval are detected to thereby obtain a pulse waveformas shown. Based on the time relationship between two of these pulsesthat occur within a unit interval, a decision is made as to whether a“0” or a “1” bit is expressed in that unit data section.

[0011] An alternative method of using a wobble signal has been proposedin Japanese patent Laid-open No. 2001-2099237, whereby each ofsuccessive unit intervals of the wobble signal is modulated to haveeither a 0° or 180° phase, in accordance with whether the intervalexpresses the “1” or the “0” bit state. In the following, such phasemodulation intervals of the wobble signal are referred to as unit datasections. During playback of the wobble signal, a sampling clock signalis generated which is locked in phase and frequency with the playbackwobble signal, and which is used to generate sampling pulses for use inperforming synchronous detection of the wobble signal, i.e., by samplingsuccessive periods of that signal. The resultant sample values that areobtained for a unit data section are successively integrated, to obtaina final value (phase integration value), whose amplitude is indicativeof the phase of the wobble signal within that unit data section. In thatway, discrimination of the “1” and “0” bit states expressed in theplayback wobble signal can be performed based on the levels of the phaseintegration values obtained for respective unit data sections.

[0012] This method is illustrated in the timing diagram example of FIG.9, in which in addition to the aforementioned sampling pulses,information detection timing pulses are derived from synchronizinginformation (i.e., a synchronizing pattern) recorded on the opticaldisk. The information detection timing pulses define respectiveintervals in which integration is performed of the sample values thatare obtained for one unit data section. At the end of each informationdetection timing pulse, a decision is made as to whether a “0” or a “1”bit is expressed, based on the phase integration output level which hasbeen attained at that time.

[0013] In addition to two unit data sections which express the “1” and“0” bit states respectively, the diagram of FIG. 9 shows a referencewobble section of the wobble signal, whose function will be describedhereinafter.

[0014] However as increasingly high values of recording density areachieved for optical recording media, so that the track pitch isreduced, the signal/noise ratio of the playback signal becomes lowered.Specifically, if phase modulation of the wobble signal is utilized asdescribed above, then as the track pitch is reduced, there is anincreasing degree of crosstalk in the playback wobble signal, due to thewobble of adjacent tracks. This results in deterioration of the wobblesignal and phase inversions of the wobble signal may also occur, so thatthe accuracy of synchronous detection of the playback wobble signal isreduced, and the accuracy of demodulation may thereby be reduced.

[0015] These problem become more severe if there is any deterioration ofthe optical recording medium.

[0016] It should be noted that such problems are not limited to methodsin which modulation is performed by alteration of the phase withinrespective unit intervals. The waveform diagram of FIG. 9 illustrates amethod whereby a fundamental wobble signal frequency has a fixedproportion of a component at twice the fundamental frequency addedthereto, or subtracted therefrom, to express the “1” and “0bit states.However with such a method, crosstalk of the superimposed frequencycomponent having twice the fundamental frequency may occur from adjacenttracks, and result in errors in detection of the “1” and “0” bit statesfrom the playback wobble signal.

[0017] In an attempt to reduce this problem, in the case of the phasemodulation method illustrated in FIG. 9, sections referred to in thefollowing as reference wobble sections are provided in the recordedwobble, with each reference wobble section immediately preceding asequence of unit data sections which constitute actual recordedinformation, such a sequence being referred to in the following as adata wobble sequence. A reference phase integration value is obtainedfrom each reference wobble section in the playback wobble signal,corresponding to a specific predetermined bit state. Thus by comparingeach (final) phase integration value that is obtained in the unit datasections of a data wobble sequence with the reference phase integrationvalue of the preceding reference wobble section, it becomes possible tomore accurately discriminate between the “1” and “0” bit states.

[0018] However it is found in practice that such a countermeasure, initself, is not sufficient to overcome the above-mentioned problem ofinsufficient accuracy of demodulating the playback wobble signal, i.e.,problems in accurately discriminating between the “1” and “0” bit statesexpressed in respective unit intervals of the wobble signal, arisingfrom increasing recording density on the optical recording medium. Asillustrated in the example of FIG. 9, there is an offset in the levelvalues that are obtained for the reference phase value and for thereference phase values that are obtained in the unit data sections ofthe data wobble sequence and this, together with the problem ofcrosstalk that produces distortion of the playback wobble signal andphase inversions in that signal, makes it difficult to achieve accuratedemodulation of the information that has been recorded by phasemodulation of the wobble.

SUMMARY OF THE INVENTION

[0019] It is an objective of the present invention to overcome the aboveproblems of the prior art, by providing a wobble information detectionmethod and apparatus whereby even if there is deterioration of anoptical recording medium having the wobble recorded thereon, ordistortion and/or phase inversions of a playback wobble signal that isobtained from the optical recording medium, it becomes possible toaccurately demodulate the wobble signal by reliably discriminatingbetween “1” and “0” bit states expressed in respective unit datasections of the wobble signal, through use of a phase integration valuethat is obtained from a reference wobble section of the wobble signal,whereby a data wobble sequence containing data expressed by phasemodulation of the wobble signal can be accurately and stablydemodulated.

[0020] To achieve the above objective, it is a basic feature of theinvention that discrimination of the binary value expressed by a unitdata section of the wobble signal is based upon whether or not thepolarity of a reference phase integration value derived from a referencewobble section is identical to the polarity of a phase integration valuethat is derived for that unit data section.

[0021] More specifically, according to a first aspect, the inventionprovides a wobble information detection method for an optical recordingmedium which has synchronizing information recorded at predeterminedintervals along a track of the optical recording medium, the track beingformed with a wobble which is phase modulated to record information in aplurality of sections including at least one reference wobble sectionwhich expresses a predetermined one of two different binary values and aplurality of successive unit data sections constituting a data wobblesequence, each of the unit data sections expressing one of the binaryvalues, with the method comprising steps of

[0022] performing playback of the optical recording medium to obtain awobble signal from the wobble of the track,

[0023] operating on the wobble signal to generate a synchronizing signalthat is synchronized with the wobble signal,

[0024] sampling the wobble signal, using the synchronizing signal, toperform synchronous detection and thereby obtain successive samplevalues of the wobble signal,

[0025] detecting the synchronizing information, based on the samplevalues,

[0026] defining a series of phase integration intervals, occurring atrespective timings determined based on the synchronizing information,

[0027] initializing a phase integration value to zero,

[0028] during a phase integration interval within the reference wobblesection in the wobble signal, successively incrementing the phaseintegration value by sample values which are obtained during the phaseintegration interval, to obtain a reference phase integration value,

[0029] storing the reference phase integration value,

[0030] initializing the phase integration value to zero,

[0031] during each of respective phase integration intervals within theunit data sections of the data wobble sequence, successivelyincrementing the phase integration value by sample values which arederived during the phase integration interval, to thereby obtain a phaseintegration value corresponding to each unit data section, andinitializing the corresponding phase integration value to zero prior toa phase integration interval of a subsequent one of the unit datasections,

[0032] for each of the unit data sections, comparing the polarity of thecorresponding phase integration value with the polarity of the referencephase integration value, and

[0033] judging the respective binary values expressed by the unit datasections, based upon results of the comparison.

[0034] Alternatively, rather than performing such a polarity comparisonoperation, the invention provides such a method whereby for each of theunit data sections, the absolute difference value between the referencephase integration value and the above-mentioned corresponding phaseintegration value obtained for that unit data section is calculated.That absolute difference value is then compared with a predeterminedthreshold value, and the binary value expressed by that unit datasection is then judged based on the results of the threshold valuecomparison.

[0035] The invention further provides a wobble information detectionapparatus for detecting wobble information on an optical recordingmedium which has synchronizing information recorded at predeterminedintervals along a track of thereof, the track being formed with a wobblewhich is phase modulated to record information in a plurality ofsections including at least one reference wobble section which expressesa predetermined one of two different binary values and a plurality ofsuccessive unit data sections constituting a data wobble sequence, eachof the unit data sections expressing one of the binary values, theapparatus including optical pick-up means for producing a wobble signalcorresponding to the wobble during playback of the optical recordingmedium,

[0036] wherein the apparatus comprises:

[0037] synchronizing signal generating means for operating on the wobblesignal to generate a synchronizing signal that is synchronized with thewobble signal,

[0038] synchronous detection means for performing synchronous detectionof the wobble signal to thereby obtain successive sample values of thewobble signal,

[0039] phase integration interval setting means for detecting thesynchronizing information, based on the sample values, and for defininga series of phase integration intervals occurring at respective timingsthat are determined based on the synchronizing information,

[0040] means for initializing a phase integration value to zeroimmediately prior to each of the phase integration intervals,

[0041] memory means for storing a reference phase integration value

[0042] phase integration means functioning during a phase integrationinterval within the reference wobble section in the wobble signal tosuccessively increment the phase integration value by sample valueswhich are derived during the phase integration interval, to therebyobtain a reference phase integration value and supply the referencephase integration value to the memory means to be stored therein, andfunctioning during each of respective phase integration intervals withinthe unit data sections of the data wobble sequence to successivelyincrement the phase integration value by sample values which are derivedduring the phase integration interval, for thereby obtaining a phaseintegration value corresponding to each unit data section,

[0043] comparator means for comparing respective polarities of thecorresponding phase integration values with a polarity of the referencephase integration value, and

[0044] judgement means for judging respective binary values expressed bythe unit data sections, based upon results of the polarity comparisons.

[0045] Alternatively, instead of providing such polarity comparatormeans, such an apparatus may include means for calculating the absolutedifference value between each of respective phase integration valuesobtained for the unit data sections and the reference phase integrationvalue, with each absolute difference value being compared with a fixedthreshold value, to thereby discriminate the respective binary values.

BRIEF DESCRIPTION OF THE DRAWINGS

[0046]FIG. 1 is a system block diagram of a first embodiment of a wobbleinformation detection apparatus;

[0047]FIGS. 2A, 2B constitute a flow diagram of the operation of thefirst embodiment;

[0048]FIG. 3 is a timing diagram of the operation of the firstembodiment;

[0049]FIG. 4 is a system block diagram of a second embodiment of awobble information detection apparatus;

[0050]FIG. 5 is a timing diagram of the operation of the secondembodiment;

[0051]FIG. 6 is a partial flow diagram of the operation of the secondembodiment;

[0052]FIG. 7 is a partial view of an optical disk, showing a wobble of atrack; and

[0053]FIGS. 8,9 and 10 are timing diagrams of prior art methods ofwobble information detection.

DESCRIPTION OF PREFERRED EMBODIMENTS First Embodiment

[0054]FIG. 1 is a block diagram of a first embodiment of an optical diskapparatus which incorporates a wobble information detection apparatus.In FIG. 1, an optical disk 1 has track wobble recorded thereon asdescribed above, the wobble being phase-modulated as sections thatexpress a synchronizing pattern (synchronizing information), referencewobble sections that convey reference wobble information, and datawobble sequences which convey information such as track addressinformation. Numeral 2 denotes an optical pick-up, numeral 4 denotes adisk motor for rotating the optical disk 1, numeral 4 denotes a servocontrol circuit for controlling driving of the optical pick-up 2 androtation of the spindle motor 3, numeral 5 denotes a playback amplifierfor amplifying an optical readout signal (i.e., the playback wobblesignal) from the optical pick-up 2, and numeral 6 denotes an equalizercircuit for reducing code errors caused by waveform distortion of theplayback wobble signal from the playback amplifier 5 due to crosstalk. Awaveform shaping circuit 7 converts the waveform of the output wobblesignal from the equalizer circuit 6 to a pulse signal, and a PLL circuit8 generates a basic frequency signal that is synchronized with thewobble signal. The PLL circuit 8 can for example utilize a VCO (voltagecontrol oscillator), etc., as is well known.

[0055] A synchronous detection circuit 9 performs sampling of the wobblesignal, at timings synchronized by an output signal from the PLL circuit8, to derive successive sample values. An information detection circuit10 obtains phase integration information from the sample values that arederived by the synchronous detection circuit 9, and uses the phaseintegration information to obtain information that has been recorded onthe optical disk 1 by phase modulation of the wobble (i.e., the contentsof the aforementioned data wobble sequences). A signal processingcircuit 11 operates on the information derived by the informationdetection circuit 10 to derive command signals that are supplied to theservo control circuit 4, which applies control of the optical pick-up 2and spindle motor 3 accordingly.

[0056] The main features of the present invention reside in theconfiguration of the information detection circuit 10. Thesecharacterizing features will be described in the following, referringfirst to the flow diagram constituted by FIGS. 2A, 2B showing theoperation of the embodiment of FIG. 1, and the timing diagram of FIG. 3.During playback of recorded information from the optical disk 1, asshown in FIG. 7, the light spot 52 is focused on the optical disk 1 andresultant reflected light is converted to a playback signal by theoptical pick-up 2, with that signal being amplified by the playbackamplifier 5 and processed by the equalizer circuit 6 before beingsupplied to the synchronous detection circuit 9.

[0057] The playback signal is also supplied from the playback amplifier5 to the waveform shaping circuit 7, to be converted to a pulse waveformsignal that is supplied to the PLL circuit 8. The PLL circuit 8 therebygenerates a synchronizing signal that is synchronized with the wobblesignal (steps S1, S2 in FIGS. 2A, 2B), and supplies that synchronizingsignal to the synchronous detection circuit 9, the information detectioncircuit 10 and the signal processing circuit 11. This synchronizingsignal serves as a reference clock signal for the overall system.

[0058] In the synchronous detection circuit 9, the sampling timingsignal generating circuit 21 uses the synchronizing signal to generatesampling timing pulses for use in synchronous detection, and suppliesthe sampling timing pulses to the sampling timing signal generatingcircuit 21 which thereby performs sampling of the playback signal, i.e.,synchronous detection (steps S3, S4).

[0059] Since the synchronizing signal produced from the PLL circuit 8 issynchronized with the wobble signal, the sample values that are obtainedby the sampling section 22 are inherently synchronized with the wobblesignal. As described hereinabove, the optical disk 1 has recordedthereon a wobble signal consisting of a synchronizing pattern section,reference wobble section containing reference wobble information, anddata wobble sequence conveying data content (e.g., address information,etc.) as a sequence of bits.

[0060] The wobble signal has the waveform shown in FIG. 3. As shown, asynchronizing pattern section is immediately followed by a referencewobble section, which consists of eight periods of the wobble signal andwhich in this embodiment is assumed to express a reference phase of 0°,with that phase corresponding to the “0” bit state. The reference wobblesection is immediately followed by a data wobble sequence as shown.

[0061] In the data wobble sequence, each bit is expressed by a sectionmade up of eight periods of the wobble signal in the same way as for thereference wobble section. Each such section of the data wobble sequencewill be referred to as a unit data section. With this embodiment, if thephase of the wobble signal within a unit data section of the data wobblesequence is 180°, then that unit data section expresses a “1” bit, whileif the phase within a unit data section is 0° then that unit datasection expresses a “0” bit.

[0062] The information detection circuit 10 receives the sample valuesobtained by synchronous detection of the wobble signal, from thesynchronous detection circuit 9, together with the synchronizing signalfrom the PLL circuit 8, and a phase integration circuit 31 within theinformation detection circuit 10 performs integration of the respectivephase values of the sample values (step S5), and outputs the resultantphase integration information to a detection timing signal generatingsection 32.

[0063] Within the synchronizing pattern section, the wobble signal isconfigured such as to result in a pattern of phase integration values(obtained by the phase integration circuit 31) that are different fromany phase integration values which can be obtained for the contents ofthe reference wobble section or any of the unit data sections of thedata wobble sequence. The detection timing signal generating section 32detects the phase integration values of the synchronization pattern, andthereby obtains timing information (i.e., indicative of the timing ofthe start of the reference wobble section), with that timing informationbeing supplied to the phase integration circuit 31 (S6, S7).

[0064] The phase integration circuit 31 utilizes that timing informationfor synchronization of information detection timing intervals, i.e.,respective intervals in each of which phase integration is performed toobtain a phase integration value.

[0065] In addition, the detection timing signal generating section 32supplies an initialization signal to the phase integration circuit 31,whereby the phase integration circuit 31 resets the phase integrationvalue that is produced therefrom to zero (step S8).

[0066] Since the reference wobble section immediately follows thesynchronization pattern, the phase integration circuit 31 then performsphase integration of the sample values obtained for the reference wobblesection (step S9, S10), and generates a first one of a series ofinformation detection timing pulses which define respective phaseintegration intervals. The information detection timing pulses aresynchronized based on the timing information supplied from the detectiontiming signal generating section 32 in step 7, such that the informationdetection timing pulse occur respectively within the reference wobblesection and each of the unit data sections, in succession. Specifically,an information detection timing pulse is at the high (H) level duringthe four central periods of each of the sets of six periods of thewobble signal that respectively constitute the reference wobble sectionand each of the unit data sections. Each H level interval of theinformation detection timing pulses is preceded and succeeded by aninterval at the low (L) level, having a duration of two periods of thewobble signal. It is during each L level period of the informationdetection timing pulses, and immediately before the first informationdetection timing pulse, that the phase integration circuit 31 isinitialized, to reset the phase integration value to zero as describedabove.

[0067] During each interval in which the information detection timingpulses are at the H level, when a sampling pulse goes to the H level anda sample value is thereby obtained, the phase integration circuit 31increments the phase integration value with a sample value that isinputted at that time from the synchronous detection circuit 9.

[0068] Thus during playback of the reference wobble section shown inFIG. 3, the sampling of the second to fourth periods of the wobblesignal will result in four successive positive values, which areintegrated to obtain a final phase integration value, i.e., thereference phase integration value Vref as shown (steps S9, S10, S11).

[0069] Since the phase integration value is initialized to zero beforephase integration using the sample values of the reference wobblesection begins, a positive polarity is obtained for the reference phaseintegration value Vref with the example of FIG. 3, in which the polarityof Vref has been predetermined as corresponding to the “0” bit state.

[0070] When the phase integration reference value Vref has beenobtained, and the information detection timing pulses then go to the Llevel, the detection timing signal generating section 32 supplies awrite control signal to the memory section 33, whereby the phaseintegration reference value Vref is stored in the memory section 33(steps S11, S12).

[0071] When the information detection timing pulses then go to the Hlevel after the start of the data wobble sequence, the phase integrationcircuit 31 is again initialized, so that the phase integration valueproduced from the phase integration circuit 31 is reset to zero (stepsS13, S14).

[0072] Thereafter, sampling of the second through fourth periods of thewobble signal in each of the successive unit data sections of the datawobble sequence is performed in the same manner as described for thereference wobble section, i.e., with the phase integration value beingreset to zero before phase integration of the sample values of a unitdata section begins, with sampling of the wobble signal being executedeach time the sampling pulses are at the H level during an interval inwhich the information detection timing pulses are at the H level withina unit data section, and with the four sample values thereby obtainedbeing integrated to obtain a final phase integration value for that unitdata section (steps S15, S16).

[0073] In the example of FIG. 3, the unit data section that immediatelyfollows the reference wobble section expresses a “1” state bit, and sothe phase of the wobble signal in that unit data section differs by 180°from the phase during the reference wobble section. As a result, thesample values that are obtained in the second to fourth periods of thatfirst unit data section are negative values. These are integrated toobtain the final phase integration value Vd1 for that unit data section,i.e., a negative polarity value, which is temporarily held in the phaseintegration circuit 31.

[0074] At the end of that unit data section, the detection timing signalgenerating section 32 supplies a comparison command signal to thepolarity comparison section 34. The polarity comparison section 34responds by comparing the polarity of the phase integration value Vd1with the polarity of the phase reference value Vref that was obtainedfor the reference wobble section, which is held in the memory section 33(steps S16, S17).

[0075] If these polarities are identical, then the polarity comparisonsection 34 judges that the bit state expressed by that unit data sectionis “0”. Conversely, if the polarity of the phase integration value Vd1is opposite to that of Vref, then it is judged that the bit stateexpressed by that unit data section is “1” (steps S18, S19).

[0076] It can thus be understood that with this embodiment, a decisionis made as to whether or not the polarity of the phase integration valuethat is obtained for a unit data section within the data wobble sequencediffers from the polarity of the phase reference value, to thereby judgethe bit state that is expressed by the phase-modulated wobble signalwithin that unit data section.

[0077] With the example of FIG. 3, the polarity of the reference phaseintegration value Vref (which is predetermined as corresponding to the“0” bit state) is positive, and since the polarity of the phaseintegration value obtained for the first unit data section is negative,it is judged that the first unit data section expresses a “1” state bit.

[0078] The information which has thereby been obtained by the polaritycomparison performed by the polarity comparison section 34 is outputtedto the data demodulation circuit 35. The data demodulation circuit 35responds by supplying information indicative of the “1” or “0” bit stateto the signal processing circuit 11, in accordance with the polarityjudgement information that has been received (step S21).

[0079] As a result, the “1” bit state expressed by the first unit datasection is demodulated and supplied to the signal processing circuit 11.

[0080] Thereafter, the information detection circuit 10 repetitivelyexecutes the above processing for each of the unit data sections of thedata wobble sequence (steps S22→S14 ^(˜)S21).

[0081] In the example of FIG. 3, the second unit data section expressesa “0” bit, and so is modulated with the same phase as that of thereference wobble section, i.e., 0°. After the phase integration circuit31 has been initialized and the phase integration value thereby reset tozero, phase integration is executed during that second unit data sectionin the same way as for the reference wobble section, by the phaseintegration circuit 31. As shown in FIG. 3, a final phase integrationvalue having positive polarity, designated as Vd0, is thereby obtainedfor the second unit data section, so that information indicative of the“0” bit state is supplied to the signal processing circuit 11 as thedemodulated output.

[0082] Thereafter, if the detection timing signal generating section 32newly detects a synchronization pattern, then synchronizing ofgenerating the information detection timing pulses based on thatsynchronization pattern is again performed, as described hereinabove,and the same processing as described above is performed for the nextreference wobble section (steps S23→S7 ^(˜)S21).

[0083] In that way, the signal processing circuit 11 assembles a dataset as a sequence of demodulated bits that have been supplied from theinformation detection circuit 10, and thereby obtains information suchas address information etc., that is recorded within a data wobblesequence on the optical disk 1.

[0084] The address information etc., is outputted from the signalprocessing circuit 11 to the servo control circuit 4, to be used asdrive control information for controlling the optical pick-up 2 andspindle motor 3.

[0085] As described above, this embodiment performs synchronousdetection using timing information derived from a synchronizing pattern,to obtain successive sample values indicative of respective phase valuesof the wobble signal, and performs integration of the series of samplevalues thereby derived during each reference wobble section or unit datasection to obtain respective (final) phase integration values. Thepolarity of the phase integration value thereby obtained for a unit datasection is compared with that obtained for the preceding referencewobble section (with the polarity of the phase integration valueobtained for a reference wobble section having been predetermined ascorresponding to a specific “1” or “0” bit state), to thereby judge therespective bits that are conveyed by the unit data sections of a datawobble sequence.

[0086] Such an information detection method, based on comparison ofpolarities of phase integration values, is less affected by distortionand erroneous phase inversions in the playback wobble signal, bycomparison with a prior art method whereby level comparison is performedagainst values which contain an offset. Furthermore with the aboveembodiment, reliable discrimination of the “1” or “0” bit statesexpressed by the respective unit data sections can be achieved, so thatmore precise and stable detection of the contents of a data wobblesequence, i.e., demodulation of a data wobble sequence, can be achieved.

[0087] With the above embodiment, the information detection circuit 10has been shown in block system form, as having a hardware configuration.However it will be understood that all of the processing functionsdescribed can be implemented by software, i.e., by utilizing amicrocomputer operating under a suitable control program.

[0088] In that case, the microcomputer would be provided with a ROM(read-only memory) having stored therein a program for executing theprocessing sequence of steps S5 to S23 shown in the flow diagram ofFIGS. 2A, 2B, with the CPU of the microcomputer successively executingthe program contents.

[0089] Furthermore with the above embodiment, a synchronizing patternand a reference wobble section are successively recorded on the opticaldisk, followed by a data wobble sequence. However it would be possiblefor example to also record a synchronization pattern followed by areference wobble section at one or more positions within a data wobblesequence.

[0090] Moreover although the above embodiment has been described for thecase in which the synchronization pattern is recorded on the opticaldisk 1 within the wobble, it would be equally possible record thesynchronizing pattern as a sequence of pits.

Second Embodiment

[0091]FIG. 4 is a block diagram of a second embodiment of an opticaldisk apparatus which incorporates a wobble information detectionapparatus. As can be understood by comparing FIG. 4 with FIG. 1, thesecond embodiment differs from the first embodiment of FIG. 1 in thatthe polarity comparison section 34 is replaced by a calculation section42 and a level comparison section 43, in the information detectioncircuit 41. Other components of the second embodiment which correspondto components in the embodiment of FIG. 1 are designated by identicalreference numerals to those of FIG. 1, and detailed description of thesewill be omitted. The following description will be limited to mainly theoperation of the calculation section 42 and of the level comparisonsection 43.

[0092] Firstly, when sample values of the wobble signal are obtained bythe synchronous detection circuit 9 and inputted to the informationdetection circuit 41 after the synchronization pattern has beendetected, so that the information detection timing pulses and samplingpulses are being generated with the requisite synchronized relationshipwith the wobble signal as described for the first embodiment, the phaseintegration value is reset to zero at the start of the reference wobblesection, then phase integration is performed by the phase integrationcircuit 31 using the sample values, to establish the reference phaseintegration value Vref, also as described for the first embodiment(i.e., as in steps S1 to S12 of FIGS. 2A, 2B).

[0093] The phase integration value is then again initialized to zero,and thereafter a (final) phase integration value Vd is obtained in eachof successive unit data sections in the same manner as described for thefirst embodiment (i.e., as in steps S13 to S16), with the polarity ofeach phase integration value Vd being determined in accordance with thebit state that is conveyed by the corresponding unit data section.

[0094] The characteristic feature of the second embodiment resides inthe way in which the reference phase integration value Vref and thephase integration value Vd obtained for a unit data section are used todiscriminate the “1” or “0” bit state that is expressed by that unitdata section. The overall processing flow of this embodiment thusdiffers from that of the first embodiment, shown in FIGS. 2A, 2Bdescribed above, only with respect to the judgement operations of stepsS17 to S20. FIG. 6 is a partial flow diagram showing this different partof the flow sequence, for the second embodiment.

[0095] With the second embodiment, when a phase integration value Vd isobtained for a unit data section, the detection timing signal generatingsection 32 supplies a command signal to the calculation section 42,whereby the calculation section 42 derives the absolute difference value|Vref−Vd| between that phase integration value Vd and the referencephase integration value Vref (step S31). A predetermined threshold valuedesignated as Th has been set beforehand for the level comparisonsection 43, which compares the absolute difference value |Vref−Vd| withthe threshold value Th. A decision is made as to whether that unit datasection expresses a “1” or “0” bit, based on the result of thecomparison (steps S32 to S33). The level comparison section 43 thensends information to the data demodulation circuit 35, indicative of thedecision result, with the data demodulation circuit 35 operating asdescribed hereinabove for the first embodiment.

[0096] If a reference wobble section and the unit data sections of adata wobble sequence occur in the wobble signal successively as shown inFIG. 3, then the timing relationships between the sampling pulses, theinformation detection timing pulses and the wobble signal will besimilar to that of FIG. 3, as illustrated in the timing diagram exampleof FIG. 5 for the second embodiment. In that example (in which it isagain assumed that the phase of the reference wobble section is 0° andis indicative of the “0” bit state) with the first unit data sectionfollowing the reference wobble section expressing a “1” bit (so that thecorresponding phase integration value Vd1 is negative), the absolutedifference value |Vref−Vd1| which is obtained for that first unit datasection substantially exceeds the threshold value Vth, as shown, so thatit can be accurately judged that a “1” bit is expressed.

[0097] Conversely, in the case of a unit data section for which thephase is 0° such as the second unit data section in FIG. 5, theresultant phase integration value Vd0 is positive, so that thecorresponding absolute difference value is close to zero and so issubstantially lower than the threshold value Vth, and hence it can beaccurately judged that this unit data section expresses a “0” bit. Thethreshold value Vth is preferably set as approximately (½)·|Vref′−Vd′|,to achieve reliable discrimination between the phase integration valuesexpressing the “1” and “0” bit states, where “Vref′” here signifies atypical value that would be obtained for the reference phase integrationvalue, and “Vd′” here signifies a typical (final) phase integrationvalue that would be obtained for a unit data section and which is ofopposite polarity to Vref.

[0098] In that way, accurate discrimination of the “1” and “0” bitstates expressed by the respective unit data sections can be achievedeven if phase inversion of the wobble signal occurs.

[0099] In other respects, the operation and advantages of thisembodiment are similar to those of the first embodiment described above.However due to the large amount of difference between the levels whichare judged for the purpose of discriminating between the “1” or “0” bitstates with the second embodiment, more reliable discrimination can beachieved than for the first embodiment.

[0100] With the second embodiment, as for the first embodiment, eachsynchronizing pattern is shown as being recorded in the wobble signal,immediately preceding a reference wobble section, with informationdetection timing pulses subsequently being generated based on the timingof detection of that synchronization pattern. However it would beequally possible to record the synchronization patterns as pits, along atrack, with the reference wobble sections being located at fixedpositions in relation to these pits. In that case, synchronizing of theinformation detection timing pulses and detection of the referencewobble sections could be performed based on the synchronizinginformation obtained from these pits. When the start of a referencewobble section is thereby detected, phase integration of that referencewobble section, and of each of the unit data sections of the succeedingdata wobble sequence, would then be performed in the same manner asdescribed for the above embodiments.

[0101] It should thus be understood that although the invention has beendescribed in the above referring to specific embodiments, variousmodifications to these could be envisaged, which fall within the scopeclaimed for the invention in the appended claims.

What is claimed is:
 1. A wobble information detection method for anoptical recording medium having synchronizing information recorded atpredetermined intervals along a track of said optical recording medium,said track being formed with a wobble which is phase modulated to recordinformation in a plurality of sections including at least one referencewobble section which expresses a predetermined one of two differentbinary values and a plurality of successive unit data sectionsconstituting a data wobble sequence, each of said unit data sectionsexpressing one of said binary values, wherein said method comprisessteps of: performing playback of said optical recording medium to obtaina wobble signal from said wobble of said track; operating on said wobblesignal to generate a synchronizing signal that is synchronized with saidwobble signal; sampling said wobble signal, using said synchronizingsignal, to perform synchronous detection and thereby obtain successivesample values of said wobble signal; detecting said synchronizinginformation, based on said sample values; defining a series of phaseintegration intervals, occurring at respective timings determined basedon said synchronizing information; initializing a phase integrationvalue to zero immediately prior to a phase integration interval withinsaid reference wobble section in said wobble signal and successivelyincrementing said phase integration value by sample values which areobtained during said phase integration interval, to obtain a referencephase integration value; storing said reference phase integration value;initializing said phase integration value to zero immediately prior toeach of respective phase integration intervals within said unit datasections of said data wobble sequence and successively incrementing saidphase integration value by sample values which are derived during saideach phase integration interval, to thereby obtain a phase integrationvalue corresponding to said each unit data section; for each said unitdata section, comparing a polarity of said corresponding phaseintegration value with a polarity of said reference phase integrationvalue1; and judging a binary value expressed by said each unit datasection, based upon results of said comparison.
 2. A wobble informationdetection apparatus for detecting wobble information on an opticalrecording medium having synchronizing information recorded atpredetermined intervals along a track of said optical recording medium,said track being formed with a wobble which is phase modulated to recordinformation in a plurality of sections including at least one referencewobble section which expresses a predetermined one of two differentbinary values and a plurality of successive unit data sectionsconstituting a data wobble sequence, each of said unit data sectionsexpressing one of said binary values, said apparatus including opticalpick-up means for producing a wobble signal corresponding to said wobbleduring playback of said optical recording medium; wherein said apparatuscomprises: synchronizing signal generating means for operating on saidwobble signal to generate a synchronizing signal that is synchronizedwith said wobble signal; synchronous detection means for performingsynchronous detection of said wobble signal to thereby obtain successivesample values of said wobble signal, phase integration interval settingmeans for detecting said synchronizing information, based on said samplevalues, and for defining a series of phase integration intervalsoccurring at respective timings that are determined based on saidsynchronizing information; means for initializing a phase integrationvalue to zero immediately prior to each of said phase integrationintervals; memory means for storing a reference phase integration value;phase integration means functioning during a phase integration intervalwithin said reference wobble section in said wobble signal tosuccessively increment said phase integration value by sample valueswhich are derived during said phase integration interval, to therebyobtain said reference phase integration value and supply said referencephase integration value to said memory means to be stored therein, andfunctioning during each of respective phase integration intervals withinsaid unit data sections of said data wobble sequence to successivelyincrement said phase integration value by sample values which arederived during said phase integration interval, for thereby obtaining aphase integration value corresponding to said each unit data section;comparator means for comparing respective polarities of saidcorresponding phase integration values with a polarity of said referencephase integration value; and judgement means for judging respectivebinary values expressed by said unit data sections, based upon resultsof said polarity comparisons.
 3. A wobble information detection methodfor an optical recording medium having synchronizing informationrecorded at predetermined intervals along a track of said opticalrecording medium, said track being formed with a wobble which is phasemodulated to record information in a plurality of sections including atleast one reference wobble section which expresses a predetermined oneof two different binary values and a plurality of successive unit datasections constituting a data wobble sequence, each of said unit datasections expressing one of said binary values, wherein said methodcomprises steps of: performing playback of said optical recording mediumto obtain a wobble signal from said wobble of said track; operating onsaid wobble signal to generate a synchronizing signal that issynchronized with said wobble signal; sampling said wobble signal, usingsaid synchronizing signal, to perform synchronous detection and therebyobtain successive sample values of said wobble signal; detecting saidsynchronizing information, based on said sample values; defining aseries of phase integration intervals, occurring at respective timingsdetermined based on said synchronizing information; initializing a phaseintegration value to zero immediately prior to a phase integrationinterval within said reference wobble section in said wobble signal andsuccessively incrementing said phase integration value by sample valueswhich are obtained during said phase integration interval, to obtain areference phase integration value; storing said reference phaseintegration value; initializing said phase integration value to zeroimmediately prior to each of respective phase integration intervalswithin said unit data sections of said data wobble sequence andsuccessively incrementing said phase integration value by sample valueswhich are derived during said each phase integration interval, tothereby obtain a phase integration value corresponding to said each unitdata section; for each said unit data section, calculating an absolutevalue of difference between said corresponding phase integration valueand said reference phase integration value; comparing said absolutedifference value with a predetermined threshold value; and judging abinary value expressed by said each unit data section, based uponresults of said comparison.
 4. A wobble information detection apparatusfor detecting wobble information on an optical recording medium havingsynchronizing information recorded at predetermined intervals along atrack of said optical recording medium, said track being formed with awobble which is phase modulated to record information in a plurality ofsections including at least one reference wobble section which expressesa predetermined one of two different binary values and a plurality ofsuccessive unit data sections constituting a data wobble sequence, eachof said unit data sections expressing one of said binary values, saidapparatus including optical pick-up means for producing a wobble signalcorresponding to said wobble during playback of said optical recordingmedium; wherein said apparatus comprises: synchronizing signalgenerating means for operating on said wobble signal to generate asynchronizing signal that is synchronized with said wobble signal;synchronous detection means for performing synchronous detection of saidwobble signal to thereby obtain successive sample values of said wobblesignal, phase integration interval setting means for detecting saidsynchronizing information, based on said sample values, and for defininga series of phase integration intervals occurring at respective timingsthat are determined based on said synchronizing information; means forinitializing a phase integration value to zero immediately prior to eachof said phase integration intervals; memory means for storing areference phase integration value; phase integration means functioningduring a phase integration interval within said reference wobble sectionin said wobble signal to successively increment said phase integrationvalue by sample values which are derived during said phase integrationinterval, to thereby obtain said reference phase integration value andsupply said reference phase integration value to said memory means to bestored therein, and functioning during each of respective phaseintegration intervals within said unit data sections of said data wobblesequence to successively increment said phase integration value bysample values which are derived during said phase integration interval,for thereby obtaining a phase integration value corresponding to saideach unit data section; absolute difference value calculation means forcalculating, for each of said unit data sections, an absolute differencevalue between said reference phase integration value and saidcorresponding phase integration value; comparator means for comparingeach of said absolute difference values with a predetermined thresholdvalue; and judgement means for judging respective binary valuesexpressed by said unit data sections, based upon results of saidthreshold value comparisons.